Looking for a 10K linear slide potentiometer

[Demon]

I'm looking for what Bournes refers to as B1 taper:




So far all I could find is the PTL Series slide pots with LED at Mouser:

https://www.bourns.com/docs/product-...rsn=10cbbd87_6


At $10.57 each, or $7.41 for 10, not exactly on the cheap end.

I bought a bunch of Behringer B10K slide pots from AliExpress back in August, and I just find out now in testing that they're not exactly linear. They have a slight curve to their progression; moving 1K for the first and last 1/4 of travel, and 8K within the middle 2/4s.

I had tested the center at 5K, but that only eliminates the A and C tapers. You really need to test at 1/4 and 1/2 of travel for 25% and 50% of Ohm rating (just looking for taper B is not enough). The ones I got seem to be between the B3 and B4 curve.


I'm also trying to find caps with 6mm x 2mm holes for these pots. I can't find any. I'm starting to think that audio companies use custom caps, or they don't even cover these at all.

I thought they'd use a cap with a clear/semi-transparent center cause these slide pots don't have dust covers like the Behringers.

[Ioannis]

Well, I am sure that original pots from Mouser will be much more close to the specs than what are Ali stores sell. That justifies the price also.

I had similar issues with rotary pots for amplifiers that were not tracking well (stereo pots for volume).

Why not 3D print your own caps? These parts are becoming more difficult to find.

Ioannis

[Demon]

Well, I am sure that original pots from Mouser will be much more close to the specs than what are Ali stores sell. That justifies the price also....

I have no doubt the Mouser/Digikey/Newark parts are top quality, but in the end, I have a limited budget. I just don't need the built-in LED on the PTL Series. It's super cool, but I don't need it. I sent all 3 an email asking them for an ordinary 100mm B10K slide pot.

I was also looking at the PTB Series, but it doesn't have any taper graph. It just says linear, audio in the specs at top left. And that's exactly how I got nailed with the taper B Behringers. I'm not falling for that again.

https://www.bourns.com/docs/Product-Datasheets/PTb.pdf


I also sent an email to Bourns, asking them for a taper chart for the PTB Series. I have no idea if/when they'll respond.

...
I had similar issues with rotary pots for amplifiers that were not tracking well (stereo pots for volume).
...

I bet you had one of those taper B with a slight curve like B3, B4 and B5. Check the chart on page 4:

https://www.bourns.com/docs/Product-Datasheets/PTL.pdf

...Why not 3D print your own caps? These parts are becoming more difficult to find.

Generally, PLA plastic is not as solid as the plastic on commercial caps, and it degrades quicker under UV rays (lamps, sun, etc). I've seen reports PLA can start degrading in 1 month, to 12 to 18 years; all depending on environment. I can't take that sort of chance.

I still have to study what other plastics I can use. ABS is extremely solid, but it's a bit more finicky to use, and requires adequate ventilation. I still haven't looked at the other plastics yet.

If I can find a slide pot with a 4mm shaft, then I'm ok. I've seen a few 6mm caps on sale. But yeah, at worse I'll fabricate my own.

I'm already fabricating my case, and most likely will be using ABS. So it seems like I'm not going to have much choice. It's not like I can put a warning DO NOT PUT IN DIRECT SUNLIGHT, OR UNDER UV LAMPS OR ANYTHING THAT CAN DEGRADE PLA PREMATURELY.

[Ioannis]

I suppose, if the product is not very well made, manufacturers might hide some of the specs!

For a pot most will think it is not too much important to know such details...

Putting a label like that "DO NOT PUT IN DIRECT SUNLIGHT, OR UNDER UV LAMPS OR ANYTHING THAT CAN DEGRADE PLA PREMATURELY" I am pretty sure would go viral!

Ioannis

[Demon]

...Putting a label like that "DO NOT PUT IN DIRECT SUNLIGHT, OR UNDER UV LAMPS OR ANYTHING THAT CAN DEGRADE PLA PREMATURELY"

I am pretty sure would go viral!...

I'm not sure I'd like to go viral for that reason.

[Demon]

Well, I found even better than buying from AliExpress. A manufacturer just offered me a deal at my exact specs 17.5 times less expensive than North American prices.
:O

She reduced her MOQ because I already bought SR25 rotary switches from them.

[Ioannis]

I really hope that these pots are in fact true linear B1 curve ones.

Nice offer!

Ioannis

[Demon]

I hope so. She gave me a chart and it's pretty much in line with what Bourns offers for straight B taper.

If you look at their PTL and PTA datasheets, Bourns has a taper chart, but nothing in the PTB datasheet. It took Bourns something like 2 weeks to send me that chart.




By the way, I was in talks with one manufacturer that identified their slide pots by PTB. I didn't go with that one; their price was just a bit higher than "the chosen one".

[Ioannis]

Big companies, big delays!

Hope that the chinese one works as it should be. Wish you luck.

Ioannis